Engine starter



May 30,1944. Jfw. mz ERALD 2,350,304

ENGINE STARTER Filed Aug. 1, 1941 D MMG ff 4 Patente-d May 30, 1944- f www lpurifi-3D STATES TENT orarie-s -4 .301m wrm Gerald, M

Briggs & Stratton Application August 1, 1941,*fseriai No'. 405,016

This inventionrelate's'to engine startersof the type'wherein the pinion isfautor'natically propelled into mesh with the ring gear of the, engine -and automatically'retractedupon starting of the engine.

In vengine starters of `this type it has always b'eennecessary to lprovide vsome means of preventing-the pinion from'drifting vor creeping forilwaukee, Wis., assignorfto Corporation, Milwaukee, /Wis., a corporation of Delaware wardly intoengagement with-the ring gearwhile the engine is running. It is also necessary, especially with high-speed engines, to provide some means ofV preventing rebound 'of the ypinion during its retraction. j

Various' expedients have been employed in the past for 'guarding lagainst these twoobjectionable occurrences, but heretofore 'there has.`

been `no means by which both' were eliminated with the same mechanism. It iis, therefore, an object of this invention to provide an yengine starter having a brake kmechanism which applies alight force to holdthe pinion against drifting or creeping forwardly 'and' exerts a strongerforceto prevent rebound during retraction of the pinion. y

Another object o'f this invention is the provision of a brake mechanism so designed that the centrifugal force which obtains during revolution of the pinion as it is being retracted applies a braking force proportional to the speed of rotation of the pinion.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described, and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of the physical' embodiment of the invention constructed in accordance with the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a view in side elevation of an engine starter embodying this invention, part of the pinion sleeve being broken away;

Figure 2 is a cross sectional view taken through Figure 1 on the plane of the line 2-2 and showing the manner in which the. brake mechanism serves as an anti-creep detent;

Figure 3 is a view similar to Figure 2 but showing the brake mechanism in its position it occupies during retraction of the pinion; and

Figure 4 is a perspective view of the starter mechanism 'forwardly o'fl'the ures 2v and 3 l'are taken.

Referring now particularly to the vaccompanying drawing, invvhich'lilse numerals indicate'like parts, the numeral 5 designates the shaft of va starter motor upon vwhich the starter mechanism indicated generally bythe numeral 6 is mounted. The starter mechanism includes a pinion l arranged to move from a retracted-'position shownl inFigure 1 into'mesh with 'an'engine ring -gear A8. l l

The details of the starter mechanism'as to the manner in'whichl it is mounted on the vsha-ft and the vmanner-in which torsional and endwise resiliency are obtained form no part of this invention and thus have not be'enshown.l vFor these features reference may be had -to patent No. Re. 20,686, issued to John W. Fitz Gerald April '5; 193,8.

pianey on which Fie- Longitudin'al translation :of ithe pinion to and from operative Vdriving position in' mesh with the ring gear results from"relative rotation between the pinion andan actuating member '9. The actuating member is driverrfrom the starter shaft through a 'torsionally and jendwise resilient driving connection v(not shown) and is vexternally threaded to receive an internally threaded sleeve I0 on the pinion.

Near its base or rear end, the threads of the actuating member 9 are cut down to form a groove Il. This groove coacts with a brake member I2 to a provide an anti-drift oranticreep detent which serves to hold the pinion against drifting forwardly into mesh with the ring gear while the engine is running.

The brake member I2 is a lever medially pivoted as at I3 to an annular flange I4 carried by the pinion sleeve. One end I5 of the lever is lighter than its other end I6. The light end passes through an opening I'I in the wall of the sleeve Ill to engage the threads of the actuating member and enter the groove II when the pinion is fully retracted.

A light spring I8 confined between the heavy end I5 of the lever and the bottom of a socket I9 in the adjacent portion of the sleeve Wall yieldingly imparts a turning moment on the lever member in a direction to engage its end i5 with the actuating member; but it is to be observed that the braking force applied by means of this spring is no greater than that heretofore in use in engine starters for the purpose of preventing the pinion from drifting or creeping forwardly.

During forward translation of the pinion when it is being advanced into mesh with the ring gear the inertia of the pinion theoretically holds the pinion against rotation while the actuating member revolves within it. In actual practice, the pinion may revolve slightly but for all intents and purposes the pinion does not turn during its forward propulsion. Hence, the force acting on the brake mechanism is only that of the light spring I8.

However, at the time the engine starts, the pinion is revolving at a speed in excess of that of the actuator, and as a consequence retrograde translation of the pinion to its retracted position shown in Figure 1 takes place".V

The differential in speed of rotation betweenA the pinion and actuating member is so great especially with high speed engines that unless some means were provided to hold the pinion in its retracted position it would strike the base of the actuating member and bounce back toward the ring gear. In the past efforts were made to prevent this objectionable condition by means which would grip the pinion or its sleeve the instant retraction was completed. In other words, these past expedients did not prevent rebound. They; merely limited it.

The present invention actually eliminates or prevents rebound by retarding the speed of rotation of the pinion during its retraction. This is accomplished by the simple expedient of so proportioning the weight of the lever that centrifugal force acting thereon rocks the lever in thedirection to press its end I5 against the threads of the actuating member. Hence, the faster'the pinion revolves, braking action.

YFrom the foregoing description taken in connection with the accompanying drawing, it will be readily apparent that this invention provides an exceedingly simple manner of preventing rebound in automatic engine starters and of combining this function with that of an effective anti-drift or anti-creep device.

What I claim as my invention is:

1. In an engine starter having a power driven the 1greater will be the :j

, creeping of the pinion out of its retracted position, said braking means having a centrifugally responsive part integral with said portion operable to increase the braking action of said portion upon the power driven member by an amount proportionate to the speed of rotation of the pinion.

2. In an engine starter having a pinion provided with an internally threaded sleeve, and an externally threaded actuating member on which the pinion sleeve is threaded so that relative rotation between said parts eiects longitudinal translation of the pinion from retracted position to operative position and vice versa depending upon the Adirection of relative rotation; an outward ange intermediate the ends of the internally threaded sleeve; a medially pivoted lever mounted on the ange, one end of the lever being engageable with the thread of the actuating member through a hole in the wall of the sleeve to-,retard translation of the pinion, and the opposite end of the lever being heavier so that centrifugal force incidental to rotation of the pinion acts thereon to press the first-named end of the lever, against the actuating member; and a light spring acting on the pivoted lever in a direction to engagesaid first-named end of the lever with the threads of the actuating member so as toat all times maintain a light braking action suihcient merely to hold the pinion against drifting.

JOHN WJFITZ GERALD. 

